A typical motor grader has two front traction wheels (a left and a right) which can lean relative to neutral to one side or the other such that each front wheel assumes a present wheel-lean angle from neutral. Wheel-lean is provided in order to counteract lateral forces (i.e., side-draft) caused by a moldboard angle of the moldboard of the motor grader.
Moldboard angle may be used in a variety of applications, ditching (i.e., cutting a ditch) and road maintenance (e.g., snow removal) being but two examples. Ditching typically involves large lateral forces, more so than typical road maintenance involving less material, and thus calls for more wheel-lean than road maintenance. For example, it is known for an operator to perform a first job at a first job site (e.g., ditching) using wheel-lean at a first wheel-lean angle, transition to a second job site with zero wheel-lean (e.g., traveling over the road), and perform a second job at a second job site (e.g., road maintenance) with wheel-lean at a second wheel-lean angle different from the first wheel-lean angle. Wheel-lean is sometimes changed when turning between passes to sharpen the turn. Wheel-lean is also used to make small steering corrections.
Neutral for a front traction wheel may assume a variety of orientations. It is known for neutral to be a normal to the surface on which the front wheels are positioned (e.g., the ground), the normal being vertical in the case of a flat, horizontal surface. Positive or negative camber can also be used.
The front wheels of a typical motor grader are leanable from neutral in order to change a present wheel-lean angle of the front wheels. With respect to each front wheel, a zero present wheel-lean angle means that the center-line of the wheel running through the top and bottom of the wheel is at neutral such that the present wheel-lean angle of the wheel relative to neutral is zero degrees. A non-zero present wheel-lean angle means that the wheel center-line is leaning or angled laterally to the left or right from neutral.
In some cases, the front wheels may be connected to one another for coordinated wheel-lean of the front wheels. For example, some motor graders have a front axle coupled pivotally to the main frame of the front section of the motor grader. At each end of the front axle is a yoke coupled pivotally to the axle. The left and right yokes are coupled pivotally respectively to left and right spindles using respective upper and lower kingpins. The left and right spindles are fastened respectively to left and right final drives, which are, in turn fastened respectively to the left and right front wheels. A hydraulic wheel-lean cylinder is coupled pivotally to the front axle and to, for example, the left yoke. The front wheels are connected to one another via a wheel-lean bar coupled to the yokes such that extension or retraction of the wheel-lean cylinder causes the present wheel-lean angles of the front wheels to change. The front wheels are thus coupled to opposite ends of a front axle to move relative thereto to lean at a present wheel-lean angle from neutral.
A human operator can control wheel-lean from the operator's station with an input device (e.g., a control lever), which may be operatively connected to a controller. One example system and method for manually controlling the angle of wheel-lean is described in U.S. Pat. No. 8,412,420, filed Dec. 14, 2010 and entitled Wheel Lean Control, the entire disclosure of which is hereby expressly incorporated herein by reference.
In addition to wheel-lean controls, a motor grader operator may control several other machine systems and variables. In some cases, multiple machine systems must be controlled simultaneously. For example, when changing direction during a grading operation, a motor grader operator may make adjustments to one or more of the following controls: right hand blade lift, left hand blade lift, rotational orientation of the moldboard, articulation and steering of the front and rear of the vehicle, moldboard side-shift, circle side-shift, vehicle speed, and transmission gear. In some instances, the need to manage these various factors simultaneously may impose a barrier to productivity.